1. Field of the Invention
The present invention relates to an engine having a continuously variable valve timing mechanism which makes a camshaft which moves an intake or exhaust valve to retard or advance for minimizing a compression loss in a combustion chamber and reducing fuel consumption.
2. Description of Related Art
In order to improve an engine performance, reduce the fuel consumption, and improve a quality of exhaust gas, the continuously variable valve timing (CVVT) mechanism has been introduced for making a rotation phase of the camshaft to advance or retard.
FIG. 1 illustrates a schematic diagram of an engine having a related art continuously variable valve timing mechanism. Referring to FIG. 1, the engine is provided with a cylinder head 140, a camshaft 100, a variable rotation unit 110, an oil control valve (OCV) 130, and a variable valve bolt 120, wherein an advance flow circuit 122 and a retard flow circuit 124 are formed in one side of the camshaft 100.
The variable rotation unit 110 is a pulley or sprocket fixedly secured to an end of the camshaft 100 with the variable valve bolt 120.
The variable rotation unit 110 is rotated by the engine through a crankshaft and a chain or belt to rotate the camshaft 100.
And, the variable rotation unit 110 has a retard angle chamber formed therein connected to the retard flow circuit 124, and an advance angle chamber formed therein connected to the advance angle circuit 122.
When the oil control valve 130 supplies hydraulic oil to the retard angle chamber, making the variable rotation unit 110 to rotate forward relatively, the camshaft 100 is retarded, and, when the oil control valve 130 supplies hydraulic oil to the advance angle chamber, making the variable rotation unit 110 to rotate backward relatively, the camshaft 100 is advanced.
In the meantime, in order to control the oil to be supplied to the variable rotation unit 110, the OCV (oil control valve) 130 is required, as well as a solenoid valve which is an additional control element for controlling the oil control valve 130.
Along with this, a space for mounting the oil control valve 130 and the solenoid valve is required, and a flow circuit for controlling a hydraulic pressure is liable to be lengthy and complicate.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.